Models of temperament propose that central personality dimensions related to introversion-extraversion arise from individual differences in the functioning of arousal, emotional, sensory and response mechanisms. Specifically, Eysenck (1967)has hypothesized that introverts possess more reactive arousal systems than extraverts. Gray (1982) has proposed that introverts are more reactive to negative emotional signals, whereas extraverts are more responsive to positive signals. Brebner and Cooper (1974) have suggested that introverts possess more reactive sensory than response systems, with the reverse true for extraverts. The present research assesses these models through multiple, converging experiments employing a sensitive set of visual chronometric (i.e., reaction time) techniques. Subjects are engaged in a goal-oriented task, with incentive and feedback signals indicating potential and actual progress toward the goal. The incentive and feedback signals are positive, negative, or neutral in nature, designed to elicit brief emotional reactions related to hope, fear, relief, and frustration. Reactivity to these signals is assessed by presenting a simple task following the incentive or feedback cue. These tasks have been designed to isolate and assess the component arousal, response and attentional processes elicited by the emotional signals. The results will, thus, indicate whether introverts and extraverts differ in their arousal, attentional and response-related reactivity, and whether these differences depend upon the nature of the emotional signal. Additional manipulations attempt to relate these individual differences to higher level cognitive processing (evaluation and verbal regulation) and to hemispheric functioning. Thus, the results will help integrate temperament models with the more cognitive approaches to personality and with models in the field of neuropsychology.